Female Sprague-Dawley rats will be implanted with chronic EEG and EMG electrodes and with permanent cannulas into the jugular vein for drug administration. With the use of this rat model, we will extend our EEG studies of the "drug-seeking" behavior in rats self-administering morphine, methadone, or LAAM. The power spectral correlates of EEG during abstinence from morphine, methadone, and LAAM will be studied in a similar manner. Naloxone-induced abstinence will be compared to extinction-induced abstinence. The EEG and behavioral effects of acute and chronic treatments with LAAM, DiNor-LAAM and Nor-LAAM will be delineated and compared. The proposed work will also assess the potency and duration of action of long-acting antagonists following repetitive injections of morphine.